The multiplexor accepts input from attached devices in a round-robin fashion and transmit the data in a never ending pattern.

T-1 and ISDN telephone lines are common examples of synchronous time division multiplexing.If one device generates data at a faster rate than other devices, then the multiplexor must either sample the incoming data stream from that device more often than it samples the other devices, or buffer the faster incoming stream.

In TDM Sharing of the signal is accomplished by dividing available transmission time on a medium among users.Digital signaling is used exclusively.

Time-Division Multiplexing (TDM) (synchronous) is

FDM Frequency Division Multiplexing is :-

• Useful bandwidth of medium exceeds required bandwidth of channel

• Each signal is modulated to a different carrier frequency

• Carrier frequencies separated so signals do not overlap (guard bands) e.g. broadcast radio

• Channel allocated even if no data

Sharing a Medium Data Communications and Computer Networks.Under the simplest conditions, a medium can carry only one signal at any moment in time.For multiple signals to share one medium, the medium must somehow be divided, giving each signal a portion of the total bandwidth.Multiplexer and demultiplexer are used for this.

—Frequency-Division Multiplexing
—Time-Division Multiplexing (Synchronous)
—Statistical Time-Division Multiplexing, etc